A conventional valve timing adjusting device includes: a first rotor that integrally fixes the following three parts, a housing having the bearing of a camshaft, a case internally having a plurality of shoes projecting therefrom and having hydraulic chambers formed between the shoes, and a cover covering the hydraulic chambers, and that rotates integrally with a crankshaft; and a second rotor that has a plurality of vanes each dividing each of the hydraulic chambers into an advanced-angle hydraulic chamber and a retarded-angle hydraulic chamber, can relatively rotate through a predetermined angle within the first rotor, and is integrally fixed with an intake or exhaust camshaft, wherein the hydraulic pressure of an oil pump for supplying oil to the sliding portion of an engine is supplied and discharged, and this hydraulic pressure controls the relative position of the second rotor with respect to the first rotor.
In the constitution described above, when there exits no hydraulic power used at the time of engine start-up, the shoe of the first rotor and the vane of the second rotor repeat to abut on and separate from each other to cause slapping sounds. For this reason, one of the first rotor and the second rotor is provided with an engaging cavity, and the other thereof is provided with a lock pin engaging in and disengaging from the engaging cavity; and when there is no hydraulic pressure power used at the time of engine start-up, the lock pin is caused to engage in the engaging cavity by an energizing member, thus fixing the relative position between the first rotor and the second rotor to prevent the occurrence of the slapping sounds. In addition, this lock pin travels to the releasing direction by means of hydraulic power resisting the energizing force of the energizing member. During this traveling, the back pressure existing at the rear of the lock pin is discharged outside.
In this case, a minute or micro clearance is provided between the lock pin and the engaging cavity so that the cylindrical lock pin smoothly engages in the engaging cavity, and the first rotor and the second rotor can relatively rotate through a minute angle even in a lock-pin engaging state. Consequently, this minute-angle-relative rotation causes slapping sounds, and further, causes angular misalignments when the device is assembled to the engine. This is a problem when high-precise assembly is demanded.
For this reason, in order to prevent this minute rotation, the lock pin and the engaging cavity are given the shape of a taper, and thereby, these parts are caused to interengage without a clearance, as disclosed by JP-A-2002-004816 and JP-A-2003-328708.
Patent Reference 1: JP-A-2002-004816
Patent Reference 2: JP-A-2003-328708
The conventional valve timing adjusting device is arranged as mentioned above, thus requiring fine manufacturing tolerances or precision and the high cost of production to give the tapered shape to the lock pin and the engaging cavity. Moreover, there is a problem that the lock pin is accidentally released from the engaging cavity by the component force of the alternative force of the cam to produce slapping sounds.
The present invention has been accomplished to solve the above-mentioned problem. An object of the present invention is to provide a valve timing adjusting device capable of suppressing the accidental release of the lock pin from the engaging cavity by a simple configuration and further preventing the occurrence of slapping sounds.